REMY
AYOB
TOP CYCLIST IN THE WORLD 2018 – VIA DECOMPRESSION
SICKNESS
Remy Ayob, 25, from Sungai Lui Ulu
Langat, Selangor, who had biked across 20 countries from Malaysia since March
last year and final United Kingdom on 24 February 2018.
Talking about Decompression
Illness (DCI)
describes a range of symptoms arising from decompression of the body. DCI can be caused
by two different mechanisms, which result in overlapping sets of symptoms. The
two mechanisms are:
- Decompression sickness (DCS), which results
from metabolically inert gas dissolved in body tissue under pressure
precipitating out of solution and forming bubbles during decompression. It
typically afflicts underwater divers on poorly managed ascent from depth or
aviators flying in inadequately pressurised aircraft.
- Arterial
gas embolism (AGE), which is gas bubbles in the bloodstream. In the
context of DCI these may form either as a result of bubble nucleation and
growth by dissolved gas into the blood on depressurisation, which is a
subset of DCS above, or by gas entering the blood mechanically as a result
of pulmonary barotrauma. Pulmonary barotrauma is a rupturing of
lung tissue by expansion of breathing
gas held in the lungs during depressurisation. This may typically be
caused by an underwater diver ascending while holding the
breath after breathing at ambient pressure, ambient pressure escape from a
submerged submarine without adequate exhalation during the ascent, or the
explosive decompression of an aircraft cabin or other pressurised
environment.
In
any situation which could cause decompression sickness, there is also
potentially a risk of arterial gas embolism, and as many of the symptoms are
common to both conditions, it may be difficult to distinguish between the two
in the field, and first aid treatment is the same for both mechanisms.
Signs
and symptoms
Below
is a summary comparison of the signs and symptoms of DCI arising from its two
components: Decompression Sickness and Arterial Gas Embolism.
Many signs and symptoms are common to both maladies, and it may be difficult to
diagnose the actual problem. The dive history can be useful to distinguish
which is more probable, but it is possible for both components to manifest at
the same time following some dive profiles.
A
more detailed account of the signs and symptoms of Decompression Sickness can
be found.
Decompression sickness
|
Arterial Gas Embolism
|
|
Signs
|
||
Skin
rash
|
Bloody
froth from mouth or nose
|
|
Paralysis,
muscle weakness
|
Paralysis
or weakness
|
|
Difficulty
in urinating
|
Convulsions
|
|
Confusion,
personality changes, bizarre behaviour
|
Unconsciousness
|
|
Loss
of memory, tremors
|
No
breathing
|
|
Staggering
|
Death
|
|
Collapse
or unconsciousness
|
||
Symptoms
|
||
Fatigue
|
Dizziness
|
|
Skin
itch
|
Blurring
of Vision
|
|
Pain
in joints or muscles
|
Areas
of decreased sensation
|
|
Dizziness,
vertigo, ringing in the ears
|
Chest
pain
|
|
Numbness,
tingling and paralysis
|
Disorientation
|
|
Shortness
of breath
|
Safe versus
dangerous diving
Over the
past 20 years diving has become extremely popular, both at home and abroad.
But diving
is not without its dangers. It's vital to attend a recognised diving school for
training, and subsequently make sure that you keep your skills up to date.
Diving must
be planned and carried out in a responsible manner, making sure that first aid
equipment and relevant telephone numbers are at hand should an accident take
place.
Finally,
it's important to know the signs of decompression sickness and to be able to
give first aid to an affected diver.
What is
decompression sickness?
Decompression sickness, also
called the bends, is caused by nitrogen bubbles forming in the bloodstream and
tissues of the body.
The bubbles
occur if you move from deep water towards the surface (where the surrounding
pressure is lower) in too short a space of time.
Symptoms
occur soon after the dive has finished and, in the most serious cases, it can
lead to unconsciousness or death.
If you
suspect decompression sickness: stop the dive, initiate first aid, and summon
assistance from a specialist in divers' medicine. Treatment is 100 per cent
oxygen on site and during transportation, followed by treatment in a
decompression chamber.
What are the
symptoms?
The symptoms
of decompression sickness vary because the nitrogen bubbles can form in
different parts of the body.
The diver
may complain of headache or vertigo, unusual tiredness or fatigue. He or she may have a rash, pain in
one or more joints, tingling in the arms or legs, muscular weakness or
paralysis. Less often, breathing difficulties, shock, unconsciousness or death
may be seen.
The symptoms
generally appear in a relatively short period after completing the dive. Almost
50 per cent of divers develop symptoms within the first hour after the dive, 90
per cent within six hours and 98 per cent within the first 24 hours.
In practice this means symptoms
that appear more than 24 hours after the dive are probably not decompression
sickness.
An exception
is if the diver has travelled in an aircraft or has been travelling in the
mountains. Under these circumstances, low pressure can still trigger
decompression sickness more than 24 hours after the last dive. As a result,
it's wise not to fly within 24 hours of a deep dive.
What if you
or a friend have symptoms?
- Stop the dive and keep
calm.
- If the diver is
unconscious, give first aid.
- Summon the emergency
services immediately.
- Breathe pure oxygen if
possible.
- Avoid over-exertion.
- Drink plenty of liquid.
- Any unusual condition
after a dive could be decompression sickness. So if in doubt, get medical
help.
Why does it
happen?
Nitrogen
makes up 70 per cent of the air we breathe (in the air around us and in our diving
bottles). During a dive, large amounts of
nitrogen are taken into the body's tissues. This is because the diver is
breathing air at a higher pressure than if they were at the surface. The
quantities of dissolved nitrogen depend on the depth and duration of the dive.
The deeper and longer the dive, the more nitrogen is taken up by the body. This
does not present a problem as long, as the diver remains under pressure.As the diver
begins to ascend to the surface, the surrounding pressure falls, and nitrogen
is released from the body via the lungs when the diver breathes out.If the rate
of ascent exceeds that at which nitrogen can be released, it forms bubbles in
the blood and tissues (similar to opening a bottle of fizzy drink too quickly).To minimise
the risk of bubbles forming and divers developing decompression sickness,
various tables have been drawn up that show the relationship between a given
depth of water and the time a diver can stay down.
In addition,
divers are advised to make a safety stop every 5 metres, and not to ascend at a
pace of more than 10 metres a minute. If the dive has been deep or of long
duration, it may be necessary to stop one or more times on the way up, making
so-called decompression stops.But
following the advice of the tables is no guarantee of avoiding decompression
sickness. This is because the risk of developing decompression sickness is not
only determined by the depth and length of the dive, but also by any safety or
decompression stops. Factors such as cold, current, exertion and lack of fluid
also play a part.Personal
characteristics such as age, sex, percentage of body fat and physical condition
must also be considered. Women are more at risk of decompression sickness than men.
Similarly, the risk becomes greater the older the diver and also depends on the
level of physical fitness.
How is it
diagnosed?
In most
cases, the diving history (ie information on the number of dives, diving depth,
dive time, rate of ascent and decompressions) – as well as information on
contributory factors such as cold, current, work and the diver's physical
condition – will give some indication as to whether it could be decompression
sickness.After a
thorough examination, which includes investigating balance, coordination, sense
of touch, reflexes and muscular strength, the doctor can build up a complete
picture to evaluate whether decompression sickness is likely.The doctor
will also decide if the diver requires treatment in a decompression chamber
(also called a hyperbaric or recompression chamber).
What
measures can be taken to avoid decompression sickness?
- Dive within the limits
set out in the diving tables.
- Keep your rate of ascent
to a maximum 10 metres a minute.
- Don't plan any dives
that need a decompression stop in the water.
- Make a three-minute
safety stop at a depth of 5 metres.
- Don't dive more than
three times in one day.
- If you plan more than
one dive in one day, start by making the deepest dive first.
- If you are diving for
several days in a row, have a dive-free day after two to three days.
- Don't do any hard work
before or after diving.
- Drink lots of liquid
(ideally oral rehydration solutions) before diving. Lack of fluid due to
heat or excess alcohol is dangerous.
- Make sure you are in good
physical condition and well rested. Have regular medical checkups.
- Make sure there is an
interval of at least 24 hours between diving and travel by air or climbing
up mountains. If you have had decompression treatment, the recommended
interval before the next dive is at least 48 hours.
Recovery
after decompression sickness
Mild forms
of decompression sickness can resolve themselves without treatment or by
breathing 100 per cent oxygen at the site of the accident.
But if
there's any suspicion of decompression sickness, the diver must be examined by
a doctor. This is because, although it might not seem serious at the time, the
condition may deteriorate.
If the diver
receives treatment at an early stage, the chances of avoiding permanent injury
are good. The longer that treatment is delayed, the greater the risk of serious
consequences.
You should
take a rest from diving after treatment for decompression sickness. The length
of this rest depends on the severity of the decompression sickness and the
effects of treatment, and they should be discussed with a specialist in divers'
medicine.
How is
decompression sickness treated?
There's no
medicine that's used as a matter of routine in treating decompression sickness.
At the
diving station and during transport
- 100 per cent oxygen by
mask, at a rate of 10 to 15 litres a minute.
- Give the diver plenty of
fluid to drink.
- Give first aid if the
diver is unconscious.
- Prevent the diver from
exerting himself or getting cold.
In hospital
and specialised centres
- A decompression chamber
is a steel tank that can be pressurised. There are decompression chambers
in various places in the UK - some of these are situated at naval centres.
The pressure in a decompression chamber can be increased by closing the
doors and pumping air in.
- During treatment for
decompression sickness, pressure is increased to correspond to the
pressure found 18m under water. In some cases, the pressure in the chamber
is set at 50 metres.
- The diver breathes pure
oxygen through a mask, which improves exhalation of nitrogen. At depths in
excess of 18 metres, and also after adequate intervals, the mask can be
removed in the chamber. Pressure in the chamber is reduced gradually until
the diver reaches surface pressure again.
- Treatment typically
lasts between five and six hours.
- Throughout treatment a
specially trained helper stays with the diver in the chamber. The diver's
condition is closely monitored by further examination of coordination and
balance, sense of touch, etc.
- If necessary, the
diver's medical specialist can join the diver in the chamber, but
otherwise takes charge of the treatment outside the chamber in
co-operation with the specially trained helper.
- After treatment, the
diver will be kept for 24 hours for observation in case his condition
deteriorates.
- In most instances one
course of treatment is adequate, but occasionally several treatments may
be needed.
- After treatment for
decompression sickness, a diver should take a rest from diving. The length
of this rest should be discussed with a specialist in divers' medicine.
Further
information
The now
outsourced charity DDRC Healthcare Diving mergency Hotline is +44 (0)7831
151523 (24 hrs in emergency, will advise and pass to the nearest acute
treatment unit if necessary. An alternative number is 01752 20999.